Need help swapping Boss Therm for Honeywell timer & heating receiver

[Mikey B]

Have no heating as thermostat is not sending signal to boiler (Diagnosed by plumber)
existing set-up is:
Honeywell 42002116-002 junction box to Boss Therm BUT2 timer and Boss therm BR1 receiver with a remote thermostat.

Now have a new Honeywell ST9400C Programmer and DT92E wireless room thermostat.

Have tried local electricians, but not interested, more than happy to do it myself but looking at Honeywell website it mentions making a note of what coloured wires go to lettered terminals, trouble is the BossTherm has numbers rather than letters so looking for advice please… I’ve attached pics of existing wiring.

Junction box:

BUT2 backplate:

BR1 receiver:

Thanks for any assistance.

 

[Mikey B]

The Honeywell website also makes mention of a C-wire, which doesn‘t appear to be on the current set-up but the grey coloured wire going from the BUT2 backplate to control box isn’t connected either end so is spare if needed.

 

[CBW]

What currently controls your hot water?

 

[Mikey B]

The Boss Therm BUT2, which hooks onto the backplate in the second pic. The new Honeywell ST has the same pins and looks as though it would hook on the same back plate ?

 

[CBW]

The Boss Therm BUT2, which hooks onto the backplate in the second pic. The new Honeywell ST has the same pins and looks as though it would hook on the same back plate ?

Apologies, I overlooked that, however the BUT2 is a single channel timeswitch - so this is for heating OR hot water only. The Honeywell ST9400C is a dual channel programmer for hot water and heating. Can probably be used, but you’d only have one side functioning.

 

[RandomGrinch]

So the BUT2 was exclusively controlling hot water and the BR1, the heating?

 

[Mikey B]

So the BUT2 was exclusively controlling hot water and the BR1, the heating?

Yes - exactly that, the BUT2 was programmed to turn on hot water 3 times per day - it did nothing else and the BR1 turned the heating on when the remote thermostat triggered - that had its own timer program.

 

[CBW]

Yes - exactly that, the BUT2 was programmed to turn on hot water 3 times per day - it did nothing else and the BR1 turned the heating on when the remote thermostat triggered - that had its own timer program.

So you need additional wiring to use the Honeywell ST9400C to control the heating to go to the wiring center, not have programmable option on the DT92E or change both for a programmable room thermostat

 

[RandomGrinch]

Yes - exactly that, the BUT2 was programmed to turn on hot water 3 times per day - it did nothing else and the BR1 turned the heating on when the remote thermostat triggered - that had its own timer program.

As @CBW says, some additional wiring is necessary if you want the ST9400C to control heating (along with the DT92E) and hot water.
We can help you do that, but it may be far simpler to look at a Thermostat such as a dual channel Hive, that combines all these functions in one unit.

 

[Mikey B]

Makes sense as the existing BUT2 has no pin in position labelled 1, has them for NL234 so that is for the second channel?

I think the extra wire is there - the grey one that isn’t currently connected ?

 

[RandomGrinch]

So you need additional wiring to use the Honeywell ST9400C to control the heating to go to the wiring center, not have programmable option on the DT92E or change both for a programmable room thermostat

For simplicity, I would probably run both the existing cables (to the BUT2 and BR1), to the ST9400C backplate, then patch the DT92E in there - it would save messing with the wiring centre?

 

[CBW]

For simplicity, I would probably run both the existing cables (to the BUT2 and BR1), to the ST9400C backplate, then patch the DT92E in there - it would save messing with the wiring centre?

Yes, probably makes sense, if they’re in the vicinity of each other.

@Mikey B - the pins are often like that, as they’re a universal back plate.

 

[Mikey B]

Thanks to you both so far, the current problem is the BR1 isn’t sending power to the backplate when the thermostat tells it to hence no heating.

I now understand that the new programmer can program both heating and HW whilst the old boss therm would only do one and that’s why we had a programmable remote thermostat.

so am I right if the new one DT92E literally sends a signal to the new programmer when it wants heat, that must mean the new programmer simply ignores that signal unless it’s within the programmed times ?

 

[CBW]

I think you’re understanding it wrong, the programmer/timer sends a signal to the thermostat/receiver and providing the thermostat is requiring heat, then sends a signal to the motorised valve which then sends a signal to the boiler all via switching. If you wanted heat (albeit no control) you could link the 2 switching wires (Lx and L1) in the BR1, remembering to safely isolate the electrics 1st.

 

[RandomGrinch]

Yes, probably makes sense, if they’re in the vicinity of each other.

@Mikey B - the pins are often like that, as they’re a universal back plate.

Sorry, I spoke before my brain had a chance to catch up!

If the cable to the BR1, is the top left hand cable and the BUT2 is the top right hand cable entering the wiring centre, the swap will be quite straightforward.

The spare grey wire would go into terminal 5 of the wiring centre (where the black wire is currently).
All the wiring to the BR1 could then be removed.

The wiring to the BUT2 could then be utilised for the ST9400C